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SYSTEMATIC NAME

IUBMB Comments

UTP:[protein-PII] uridylyltransferase

The enzyme uridylylates and de-uridylylates the small trimeric protein PII. The enzymes from Escherichia coli and Salmonella typhimurium have been wrongly identified, in some databases, as EC 2.7.7.12 (UDP-glucose---hexose-1-phosphate uridylyltransferase), from which it differs greatly in both reaction catalysed and sequence.

the uridylyltransferase/uridylyl-cleavage enzyme GlnD has a role in free-living growth and in symbiotic nitrogen exchange that does not depend on its substrates, the PII proteins. An in-frame deletion mutationglnDsm2 mutation has severe defects in regulating free-living and symbiotic nitrogen metabolismcompared to the glnBglnK double-deletion strain lacking the substrates of GlnD. Data indicate that the GlnD uridylyltransferase is required for proper regulation of nitrogen exchange in symbiosis with the host plant but that the PII substrate proteins are not involved in this regulation or that the glnD-sm2 mutation disrupts some additional activity of GlnD

nitrogen-regulation of gene transcription results from the regulation of the phosphorylation state of the enhancer-binding transcription factor NRI. Phosphorylation of NRI is regulated by a bicyclic cascade system containing four regulatory proteins, one of which is EC 2.7.7.59

the enzyme is constitutively expressed at a low level. The functioning of the glutamine synthetase adenylylation cascade is regulated by modulation of the activities of uridylyltransferase and adenylyltransferase, rather than by changes in the expression of their genes

GlnD of Herbaspirillum seropedicae is overexpressed with the two PII proteins GlnK and GlnB. Results show that GlnD uridylylates GlnB and GlnK trimers producing the forms PII(UMP)1, PII(UMP)2 and PII(UMP)3. GlnB is more efficiently uridylylated than GlnK

the enzyme is required for derepression of ntr-regulated promoters such as glnAp2 and pnifL, but is not involved in the nif-specific response to changes in nitrogen status mediated by the nifL products

GlnD plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of PII proteins, which in turn regulate a variety of other proteins. It is essential for NifA activation, NtrB/NtrC-regulated gene expression, and posttranslational regulation of nitrogenase activity

bifunctional uridylyltransferase/uridylyl-removing enzyme, in Rhodospirillum rubrum three PII proteins have been identified GlnB, GlnK and GlnJ, respectively, in this study it is shown that all three PII proteins are uridylylated, although the efficacy is dependent on the cation present, Mn2+ or Mg2+, respectively

bifunctional uridylyltransferase/uridylyl-removing enzyme, in Rhodospirillum rubrum three PII proteins have been identified GlnB, GlnK and GlnJ, respectively, in this study it is shown that all three PII proteins are uridylylated, although the efficacy is dependent on the cation present, Mn2+ or Mg2+, respectively

PII protein GlnK is adenylylated by GlnD in response to nitrogen limitation. In contrast to Escherichia coli, GlnK adenylylation in Mycobyceterium tuberculosis does not regulate glutamine synthetase adenylylation, nor does it mediate the transcriptomic response to nitrogen limitation

PII protein GlnK is adenylylated by GlnD in response to nitrogen limitation. In contrast to Escherichia coli, GlnK adenylylation in Mycobyceterium tuberculosis does not regulate glutamine synthetase adenylylation, nor does it mediate the transcriptomic response to nitrogen limitation

nitrogen-regulation of gene transcription results from the regulation of the phosphorylation state of the enhancer-binding transcription factor NRI. Phosphorylation of NRI is regulated by a bicyclic cascade system containing four regulatory proteins, one of which is EC 2.7.7.59

the enzyme is constitutively expressed at a low level. The functioning of the glutamine synthetase adenylylation cascade is regulated by modulation of the activities of uridylyltransferase and adenylyltransferase, rather than by changes in the expression of their genes

the enzyme is required for derepression of ntr-regulated promoters such as glnAp2 and pnifL, but is not involved in the nif-specific response to changes in nitrogen status mediated by the nifL products

GlnD plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of PII proteins, which in turn regulate a variety of other proteins. It is essential for NifA activation, NtrB/NtrC-regulated gene expression, and posttranslational regulation of nitrogenase activity

or ATP, absolutely required for in vitro uridylylation of PII proteins GlnB and GlnK. Maximum uridylylation rates for both proteins are observed in the presence of about 2 mM 2-oxoglutarate and 200-500 microM ATP. Uridylylation of both GlnB and GlnK responds to 2-oxoglutarate levels, but only GlnB responds effectively to variation on ADP/ATP ratio

maximum uridylylation rates for both PII proteins GlnB and GlnK are observed in the presence of about 2 mM 2-oxoglutarate and 200–500 microM ATP. Uridylylation of both GlnB and GlnK responds to 2-oxoglutarate levels, but only GlnB responds effectively to variation on ADP/ATP ratio

or ADP, absolutely required for in vitro uridylylation of PII proteins GlnB and GlnK. Maximum uridylylation rates for both proteins are observed in the presence of about 2 mM 2-oxoglutarate and 200-500 microM ATP. Uridylylation of both GlnB and GlnK responds to 2-oxoglutarate levels, but only GlnB responds effectively to variation on ADP/ATP ratio

null glnD mutations are introduced into the genome, but can not be stably maintained unless a second mutation is present which results in deregulated glutamine synthetase, for example: spontaneous mutation MV71, probably in gene glnE, adenylyltransferase, and introduced mutation Y407F in gene glnA, glutamine synthetase, can stabilize the glnD null mutation

a GlnKY51F protein mutant strain shows no enzyme expression, irrespective of the nitrogen status; deletion mutant is impaired in its response to nitrogen shortage, mutant shows reduced growth rate in presence of limiting amounts of ammonium or urea, deletion also impairs the transcription of genes amtB and glnK within the same operon

a GlnKY51F protein mutant strain shows no enzyme expression, irrespective of the nitrogen status; deletion mutant is impaired in its response to nitrogen shortage, mutant shows reduced growth rate in presence of limiting amounts of ammonium or urea, deletion also impairs the transcription of genes amtB and glnK within the same operon

the presence of a His tag does not alter PII substrate inhibition of the uridylyltransferase activity and has little effect on the level of the uridylyltransferase activity but results in a slight defect in uridylyl removing activity. At high PII substrate concentrations, glutamine inhibition of the uridylyltransferase activity is incomplete in the enzyme carrying a His tag. In the wild-type enzyme PII brings about substrate inhibition of the uridylyltransferase activity by binding to the central HD domain of the enzyme, and that addition of an N-terminal His tag results in an altered enzyme with subtle changes in the interactions between domains such that binding of PII to the HD domain interferes with glutamine regulation of the uridylyltransferase domain

the uridylyl-removing activity is a property specifically of the central HD domain, substitutions in this domain eliminated uridylyl-removing activity, and a truncated protein lacking the N-terminal domain display uridylyl-removing activity. The deletion of C-terminal ACT domains has little effect on uridylyl-removing activity itself but eliminates the ability of glutamine to stimulate that activity. The deletion of C-terminal ACT domains also dramatically decreases uridylyltransferase activity under all conditions tested

mutant construction by transposon Tn5 insertion and by subcloning + double crossover for recombination, phenotype characterization. Mutants are unable to utilize nitrate, essential function of glnD since most mutations close to the 5'-end are lethal

the uridylyl-removing activity is a property specifically of the central HD domain, substitutions in this domain eliminated uridylyl-removing activity, and a truncated protein lacking the N-terminal domain display uridylyl-removing activity. The deletion of C-terminal ACT domains has little effect on uridylyl-removing activity itself but eliminates the ability of glutamine to stimulate that activity. The deletion of C-terminal ACT domains also dramatically decreases uridylyltransferase activity under all conditions tested

In vitro studies of the uridylylation of the three PII protein paralogs from Rhodospirillum rubrum: the transferase activity of R. rubrum GlnD is regulated by alpha-ketoglutarate and divalent cations but not by glutamine

The robustness of the Escherichia coli signal-transducing UTase/UR-PII covalent modification cycle to variation in the PII concentration requires very strong inhibition of the UTase activity of UTase/UR by glutamine